This invention relates to an arrangement for limiting the rotary speed of a shaft. Such rotary shafts can be used to meter certain performance characteristics of other machine devices; as for example, where the axial speed of a piston in a double-acting working cylinder, translated to a rotary speed of a shaft, can be regulated by controlling the rotary speed of that shaft. Still other industry applications place critical importance on the rotary speed of the shaft; as for instance, where it is necessary to control and regulate the RPMs of an electric motor. To date, one such approach to regulating the speed of rotary shaft has been to control the RPMs of the electric motor, or to tailor-make some other control to whatever drive device is rotating the rotary shaft. The problems experienced with this indirect rotary shaft speed control arrangement have been: the need to tailor-make a control arrangement depending on the type of drive device; and the inherent delay in effecting a desired speed correction on the rotary shaft, because of the control being on the drive device and not on the rotary shaft. Where a more direct rotary shaft speed limiting arrangement has been attempted, the designs have typically required a large number of components external to the rotary shaft. An example of such an arrangement can be found in German Registered Design No. 82 29 232. This arrangement uses a pressurized brake piston which acts on a brake disk secured to the rotary shaft. Such piston arrangement requires additional external valve means, and the control and adjustment switches associated with that valve means.